This tradition is not very strict at present time and Church Slavonic pronunciation is mainly used in the most frequent forms БОГ and ГОСПОДИ

You said Г in Church Slavonic was a voiced glottal fricative. But X is a voiceless velar fricative, i.e. strictly speaking they are not a pair, as they are pronounced at different locations. The true voiceless counterpart of a voiced glottal fricative is the voicelss glottal fricative /h/, which is English H.

Currently in Church Slavonic Г is a voiced velar fricative (a voiced Х)